Discuss the role of early (less than 24 hours) versus late (greater than 48 hours) CT brain imaging in intubated patients admitted to intensive care following out of hospital cardiac arrest.
Include the following headings in your answer:
a) Rationale. (4 marks)
b) Advantages and disadvantages. (6 marks)
Syllabus topic/section:
2.1.4 Cardiovascular intensive care: Cardiac arrest: L1
2.1.8 Neurologic intensive care: Brain CT: L1
2.1.20 Radiology in intensive care
Discussion:
This question was specific to the role of CT brain in the context of an OOHCA. Candidates who limited their answer to the described clinical situation performed better than those who addressed the role of CT imaging in other scenarios.
Candidates who explained the implications of early vs late CT brain using the glossary of terms (rationale, advantages and disadvantages) scored higher marks.
Careful attention to the question, including underlining the key phrases and an application of the glossary of terms, can reduce the risk of answers diverting from what has been asked.
The marking rubric is included to aid the candidate’s future study
|
Below Standard |
At Standard |
Above Standard |
|
|
a) Rationale |
Provides no rationale Or Superficial rationale not specific to the context of OOHCA |
Rationale must include identification of arrest associated with intracerebral event, AND identification of changes consistent with HIE (early and late) |
As for “at standard and includes specific details of imaging findings and how they contribute to patient care |
|
(4 marks) |
0-1.5 marks |
2-2.5 marks |
3-4 marks |
|
b) Advantages and disadvantages |
Superficial or generic advantages/ disadvantages that are not context specific |
Must address limited situations where CTH facilitates early neuroprognostication balanced with transport risk and delay to other therapy |
As for at standard and includes place in context of other neuroprognostic assessment, specific scenarios where advantages outweigh disadvantages |
|
(6 marks) |
0-2.5 marks |
3-4.5 marks |
5-6 marks |
Superficially, it does not seem like it would be difficult to meet the "at standard" threshold, as it really only calls for an appreciation of what the CT might reveal early in the process of assessing the cardiac arrest patient. The possibilities are really limited to:
However, as one prepares to write such an answer, one immediately becomes aware of the "vs"
in the middle of it, which suggests a compare and contrast sort of structure. These work better as a table, one might think; and so:
| Early CT following OOHCA | Late CT following OOHCA | |
| Rationale |
To identify a precipitating cause for the OOHCA (which could be reversible) To give an early indication of the likely severity of the HIE |
To assess the severity of radiological changes associated with HIE |
| Advantages |
Early CT is viewed as a part of neuroprognostication imaging options in the guidelines (eg. 2021 ESC/ESICM) May reveal sufficient pathology for subsequent brain death testing Could lead towards a survivable scenario if a reversible intracranial cause is identified |
The availability of CT is usually greater than the availability of MRI and EEG Good positive predictive value (i.e. can rule in HIE) When strongly suggestive CT or MRI are combined with one other clinical predictor (eg. poor motor score or absent pupillary reflex), the false positive rate drops to 0% (Youn et al, 2022). |
| Disadvantages |
May not demonstrate any findings. False hope may rise on the basis of a relatively normal CT. Some of the precipitant causes (eg. seizures) would not appear on imaging, and CT transport would delay these. The early OOHCA patient may be quite unstable, making the transport dangerous. A large number of such low yield studies could be expensive, with little benefit to the overall population |
For qualitative reporting of poor grey-white differentiation, the false positive rate is around 8% Sensitivity for predicting poor neurological outcome remains poor. Cannot replace MRI or serial examination (a "useful but less robust predictor") |
Lopez Soto, Carmen, et al. "Imaging for neuroprognostication after cardiac arrest: systematic review and meta-analysis." Neurocritical Care 32 (2020): 206-216.
Rajajee, Venkatakrishna, et al. "Guidelines for Neuroprognostication in Comatose Adult Survivors of Cardiac Arrest." Neurocritical Care (2023): 1-31.
Bertoni, M., et al. "Neuroimaging assessment of hypoxic ischemic brain injury of the adult with perfusion computed tomography." Journal of the Neurological Sciences 381 (2017): 71-72.
Sandroni, Claudio, et al. "Prognostication in comatose survivors of cardiac arrest: an advisory statement from the European Resuscitation Council and the European Society of Intensive Care Medicine." Intensive care medicine 40 (2014): 1816-1831.
Huang, Benjamin Y., and Mauricio Castillo. "Hypoxic-ischemic brain injury: imaging findings from birth to adulthood." Radiographics 28.2 (2008): 417-439.
Gutierrez, Leonardo Guilhermino, et al. "CT and MR in non-neonatal hypoxic–ischemic encephalopathy: radiological findings with pathophysiological correlations." Neuroradiology 52 (2010): 949-976.